I think it depends. The good thing about R&S is that it has greater depth on IGP and enterprise technologies which can always provide you an alround/end to end skill set, and probably a "pre-req" if you're aiming to do the CCDE at some point. If you're planning to just work on SP environments, then probably specialization is the way forward. BTW, I think that JUNOS kick ass. I went for a one week workshop with Juniper a couple of years ago and I was astonished as to how advanced their stuff is. And as with Dynamips you can use Olive to get you started. Probably time to give it a good long though ....